Abstract:Peanut-worms Sipunculus nudus are exploited as a popular seafood in international and domestic markets due to high nutritional and pharmaceutical value. In recent years, over-exploitation of S. nudus has caused that natural resource to be degraded greatly, therefore study on S. nudus respiratory metabolism needs to be carried out to better understand the culture capacity and sustainable development of S. nudus resources. The effects of suspended feed concentration (5 mg/L, 10 mg/L, 15 mg/L, 20 mg/L, 25 mg/L) and body weight S(1.58±0.48 g), M(4.90±1.06 g) and L(7.96±0.94 g) on oxygen consumption rate (OR) and ammonia excretion rate (AR) rate of Sipunculus nudus Linnaeus were studied using experimental ecology methods. The results indicated that suspended feed concentration had significant effects on OR and AR (P<0.05), and interaction of the both factors had a significant effect on OR and AR (P<0.01). When feed concentration reached 15 mg/L, the OR and AR decreased significantly. Both the OR and AR decreased with the increasing feed concentration. The relationship between OR or AR and suspended feed concentration can be represented by the cubic function y＝ax3＋bx2+cx+d, where a values of OR or AR ranged in 0.003~0.033 and 0.0003~0.004, b values ranged in –1.698~–0.053 and –0.172~–0.003, c values ranged in –1.805~18.873 and –0.326~1.972, d values ranged in –15.675~79.940 and 3.634~14.008. Both the OR and AR increased with increasing body weight. The relationship between OR and body weight can be represented by the exponential function y=aebx, where a values ranged in 8.082~20.934 and b values ranged in 0.217~0.270. The relationship between AR and body weight can be represented by the power function y=axb, where a values ranged in 1.441~3.598, and b values ranged in 0.521~0.747. The O/N value ranged from 1.26 to 10.60. The study showed that high suspended feed concentration had a negative influence on S. nudus; once it reached 20 mg/L, the OR and AR fluctuated and declined significantly
